Method of communicating between terminals using optical wireless line and mobile terminal for performing the same

Abstract

A wireless communication method between mobile terminals using visible light and a mobile terminal therefore are disclosed. The method includes: periodically transmitting device discovery signals for searching for a visible light communication device when there is a request for a visible light communication; transmitting only reference clock signals between the device discovery signals; and connecting a link to a receiving terminal to transmit data when a response signal for the device discovery signal is received from the receiving terminal.

1 . A wireless optical communication method comprising:
 periodically transmitting device discovery signals for searching for a visible light communication device when there is a request for a visible light communication;   transmitting only reference clock signals between the device discovery signals; and   connecting a link to a receiving terminal to transmit a data when a response signal for the device discovery signal is received from the receiving terminal.   
   
   
       2 . The wireless optical communication method of  claim 1 , wherein a light source used in the visible light communication device comprises a light emitting diode (LED). 
   
   
       3 . The wireless optical communication method of  claim 2 , wherein the device discovery signal and the data are signals with which a clock signal is combined. 
   
   
       4 . The wireless optical communication method of  claim 3 , wherein the device discovery signal is a signal in which a data signal representing a device discovery and the clock signal are encoded by a differential Manchester encoding. 
   
   
       5 . The wireless optical communication method of  claim 3 , wherein the data is a signal in which a data signal and the clock signal are encoded by a differential Manchester encoding. 
   
   
       6 . The wireless optical communication method of  claim 3 , wherein the device discovery signal and the data are signals with a same frequency different from a frequency of a reference clock signal. 
   
   
       7 . The wireless optical communication method of  claim 6 , wherein a brightness and a color of a light source are changed according to the frequency of the data signal and the frequency of the reference clock signal. 
   
   
       8 . The wireless optical communication method of  claim 1 , further comprising:
 after the response signal for the device discovery signal is received from the receiving terminal,   synchronizing a clock with a clock of the receiving terminal; and   performing a link negotiation for a link connection.   
   
   
       9 . The wireless optical communication method of  claim 8 , further comprising, after synchronizing of the clock, transmitting only the reference clock signal by changing a duty cycle every preset time until the visible light communication with the receiving terminal is finished. 
   
   
       10 . The wireless optical communication method of  claim 1 , further comprising:
 after transmitting of the data to the receiving terminal,   periodically transmitting link restoration signals when the response signal is not received from the receiving terminal;   transmitting only the reference clock signal between the link restoration signals; and   re-connecting the link to the receiving terminal to transmit the data when a response signal from the link restoration signals is received from the receiving terminal.   
   
   
       11 . The wireless optical communication method of  claim 10 , wherein the link restoration signals and the data are signals with a same frequency different from that of the reference clock signal. 
   
   
       12 . The wireless optical communication method of  claim 11 , wherein a brightness and a color of the light source are changed according to the frequency of the data signals and the frequency of the reference clock signal. 
   
   
       13 . A wireless optical communication method comprising:
 transmitting a response signal to a device discovery signal of searching for a visible light communication device when the device discovery signal of searching for a visible light communication device is received;   transmitting a clock signal; and   receiving data by connecting a link to a sending terminal.   
   
   
       14 . The wireless optical communication method of  claim 13 , wherein the response signal is a signal with which the clock signal is combined. 
   
   
       15 . The wireless optical communication method of  claim 14 , wherein the response signal is a signal in which a data signal representing a response and the clock signal are encoded by a differential Manchester encoding. 
   
   
       16 . A mobile terminal comprising:
 an optical transceiver to transmit and receive a signal through a visible light;   an encoder/decoder to encode and decode a data signal and a clock signal with differential Manchester codes; and   a controller to periodically transmit device discovery signals of searching for a visible light communication device and to transmit only a reference clock signal between the device discovery signals when a visible light communication is requested, and to connect a link to a receiving terminal to transmit data when a response signal for the device discovery signals is received from the receiving terminal.   
   
   
       17 . The mobile terminal of  claim 16 , wherein a light source of the visible light comprises a light emitting diode (LED). 
   
   
       18 . The mobile terminal of  claim 17 , wherein the optical transceiver comprises a clock data recovery (CDR) circuit to generate the reference clock signal. 
   
   
       19 . The mobile terminal of  claim 18 , wherein the device discovery signals and the data signals are signals with a same frequency different from a frequency of the reference clock signal. 
   
   
       20 . The mobile terminal of  claim 19 , wherein a brightness and a color of the light source are changed according to the frequency of the data signals and the frequency of the reference clock signal. 
   
   
       21 . The mobile terminal of  claim 16 , wherein the controller, after the response signal for the device discovery signals is received from the receiving terminal, synchronizes clock signals with the receiving terminal and performs a link negotiation for the link connection. 
   
   
       22 . The mobile terminal of  claim 21 , wherein the controller, after the synchronization of the clock signals, changes a duty cycle of only the reference clock signal to be transmitted every preset time until the communication with the receiving terminal is finished. 
   
   
       23 . The mobile terminal of  claim 16 , wherein the controller periodically transmits link restoration signals and transmits only the reference clock signal therebetween when a response is not received from the receiving terminal after the transmission of data to the receiving terminal, and re-connects the link to the receiving terminal to transmit the data when a response signal for the link restoration signals is received from the receiving terminal. 
   
   
       24 . The mobile terminal of  claim 23 , wherein the link restoration signals and the data are signals with a same frequency different from a frequency of the reference clock signal. 
   
   
       25 . The mobile terminal of  claim 24 , wherein brightness and a color of a light source are changed according to the frequency of the data signals and the frequency of the reference clock signal. 
   
   
       26 . A mobile terminal comprising:
 an optical transceiver to transmit and receive a signal through visible light;   an encoder/decoder to encode and decode a data signal and a clock signal with differential Manchester codes; and   a controller to periodically transmit device discovery signals of searching for a visible light communication device and when the device discovery signals are received, to transmit a response signal for the device discovery signals in the form of a signal encoded with the differential Manchester codes, to periodically transmit the clock signal, and to receive data by connecting a link to a sending terminal.   
   
   
       27 . The mobile terminal of  claim 26 , wherein a frequency of the encoded signal is different from that of the clock signal and brightness or a color of a light Source is changed due to the frequency.